Pen



FIG. 1 is an upper front left perspective view of a pen showing my new design;

FIG. 2 is a right side elevation view thereof;

FIG. 3 is an enlarged top plan view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is an enlarged bottom plan view thereof; and,

FIG. 7 is a rear elevation view thereof.

The broken lines showing a portion of the top of the clip in FIG. 3 are included for the purpose of illustrating environment and form no part of the claimed design. 

The ornamental design for a pen, as shown and described. 